There has been provided a conventional power supply configured to turn on an illumination load. The power supply includes a DC-DC converter configured to convert an input DC (direct current) voltage into a DC voltage with a desired voltage value, and a controller configured to control the DC-DC converter. Recently, there is an increasing situation in that Light Emitting Diodes (LEDs) are employed as a light source of an illumination load because of their small consumption energy and long life.
The power supply may be provided with a cooling device such as a fan, for the purpose of dissipating the heat generated by the LEDs. For example, a power supply of JP2014-60904A (hereinafter, referred to as “Document 1”) includes a DC-DC converter configured to drive LEDs and another DC-DC converter configured to drive a motor of a DC fan, and is configured to drive the DC-DC converters so as to turn the LEDs on while being cooled by the DC fan.
It is known that a load current required for activating a motor (referred to as “activation current”) is generally larger than a load current required for rotating the motor (referred to as “steady current”) at a constant rotation speed (for example, the activation current is about several to several tens of times larger than the steady current). In order to ensure the activation current, the power supply of Document 1 needs to include such a DC-DC converter for driving the DC fan that has a large maximum output current value (i.e., large output current range), leading to an increase in a size of the DC-DC converter for driving the DC fan.